For the protection against X-rays, stray radiations are to be looked into: they are (1) Off-focus radiation (2) Forward-scattered radiation (3) Back-scattered radiation (4) Leaked radiation. Screening of (1) is achieved by using the X-ray tube either with hooded anode and small slit or provided with a conical hood to limit the irradiation field. Screening of (2) is by using a lead blind at the back of irradiated object. The radiation (3) is effectively reduced either by making the field as small as possible and by using a filter appropriate to the working voltage and thickness of the object or by covering the object with metal such as Al, Fe, Ti or Pb. The latter utilizes the difference in quality and intensity of secondary X-rays by different materials. To the screening of (4), the case of protection against direct beam described in the previous Report 2 is applied.
The rates of dissolution in normal and tangential directions to (111) surface of silicon single crystal are observed under various conditions in order to find out the relation between the geometrical forms of dissolved surfaces and the rates of dissolution in the two directions. Si specimens used are N type discs of approximately 0.3, 4 and 100 Ω•cm. The principal solutions used are composed of HNO3, HF, and H2O or NaOH and H2O. Many additional substances, for example, CH3COOH, HCl, H2SO4, H3PO4, CrO3, Br2, AgNO3, Hg2(NO3)2, Hg(NO3)2, Au(NO3)3HNO3 Pb(NO3)2 and NaNO2 are used. Experiments under special conditions such as irradiation or interruption of light were not undertaken. The rates of dissolution in the two directions and the ratio of the rates are given as functions of temperature and composition of the solution. The value of this ratio corresponds to that of tan θ given in YAMAMOTO'S work on the formation of etch pits on crystals. In the range studied, maximum values of θ are about 50° in the system HNO3-HF-H2O and about 88° in the system NaOH-H2O. It is found that the value of θ has a close relation to the geometrical form (microstructure) of dissolved (111) surface.
A new type radon meter is devised. Double wire netting is used for the external walls of the ionization chamber, and a vibrating reed electrometer and a self-recording ammeter measure the ionization current. Natural leak is very small and ions in flowing gas do not affect the ionization current density, which makes direct measurement of quickly decaying radioactive gases, thoron for example, and continuous observation of atmospheric radioactivity possible. Comparison between the bubbling method and the boiling method for measuring the concentration of radon gas from standard radium solution is made, for thorough exhaustion of the gas is of great importance. In principle, the boiling method is superior, but as to the reproducibility, no difference is found so far. Absorption of activated charcoal is applied for obtaining non-radioctive air. The charcoal proved to be almost perfect in trapping radon gas. Brief description is given of the results of atmospheric radioactive observations made with the author's radon meter and an ordinary electrostatic precipitator.
Roughness of planed surfaces of ten different kinds of wood is measured with Yamamoto contact pin type surface tester. From cumulative distribution curves obtained by calculation, these surfaces are made into three groups. Perception of roughness by touch heightens in proportion to the average height of roughness whereas these three groups do not follow this rule of linearity. Size and pitch of openings of large vessels are inferred to be attributed to this deviation. For idealization of planed wood surface, glass plates are used on which parallel streaks of various widths and pitches are etched with hydrogen fluoride. These plates may serve as standards of surface roughness of planed wood, for the perceived roughness of the two is the same.
Oriented thin films of aliphatic amines formed on metal surfaces are investigated by means of electron reflection. According to the diffraction patterns obtained, degree of regularity of orientation is roughly proportional to the molecular weight or to the chain length of the amines. Regularly oriented patterns are not observed on metal surfaces smeared with amines of less than C8. Behavior of aliphatic acids, alcohols, an damines at metal-oil boundary is also investigated by the trasmission method. Among them, aliphatic acids seem to be the only kind that exhibit regular orientation.
Effects of 1 MeV electron bombardment on conductivity of thin germanium single crystals originally about 10 ohm-cm n-type, 2 ohm-cm p-type and 40 ohm-cm undoped are studied. The observed initial carrier removal rates were 0.086 cm-1 for n-type at 215°K, 0.15cm-1 at 115°K and 0.051cm-1 for p-type at 210°K. For undoped germanium, an increment of carriers was observed. If referred to hole, 0.003cm-1 was obtained as the rate at 210°K which agrees with the rate of introduction of holes in n-type sample. From the rates of carrier removal or introduction per displacement which was calculated by using the model of SEITZ and KOEHLER, the energy level scheme is estimated as following: an electron trap, 0.12 eV below conduction band obtained at 215°K, but 0.062 eV was obtained at 115°K; an acceptor, 0.28 eV above valence band at 210°K; a hole trap, 0. 073 eV above valence band at 210°K.
On the shape of derivative curve which is conceivable to be formed by superposition of a broad and a narrow absorption band the following results were obtained: A pair of peaks of the inner component disappears when r, i.e. the ratio of peak-height of the narrow band and the height of the level at the same point, amounts to 0.73 and 0.44 for the Gaussian and the Lorentzian line shapes, respectively. For the modulation effect the distance, at which the inner peaks disappear, is approximately given by d/_??_, where d is the distance of the peak and r' the ratio of height at the inner peak point. On the symmetrical doublet line, where the distance between the peaks is given by 2. These peaks disappear when the half width increases beyond 2 and 2_??_ for the Gaussian and the Lorentzian, respectively. The observed derivative curve tends to show a single line when the modulation width exceeds 1.3 times of the peak-to-peak distance, while variation of the derivative curve is fractionally small so far as the modulation width is approximately half of the distance. Furthermore, the modulation effect for the derivative curve of a single line was studied experimentally.
The uncertainty of measurement of spectral reflectance results from recurrent and random fluctuations such as caused by slit width and stray-energy effects and photometric-scale and wavelength-scale effects. By the theory of propagation of errors, colorimetric errors propagated from spectral reflectance measurement are calculated for two color difference units. The results are shown for colors in real chromaticity regions on three luminous reflectance levels. From such results, it is found that the spectrophotometric colorimetry of samples of low luminous reflectance induces considerable amount of colorimetric error.
Investigation is made about the characteristics of light scattered by optical glasses. With a light scattering photometer, the absolute intensity, depolarization, dissymmetry of scattered light and fluorescence of optical glasses are measured. It is found that the intensity of scattered light is related with their chemical compositions, depolarization is small, fluorescence is neglegible, and dissymmetry is about 1. These phenomena show that optical glasses have characteristics of supercooled fluid. With a high temperature thermostatic arrangement, the temperature dependence of the intensity of scattered light is measured. The intensity is found to decrease with the rise of temperature. These results may be explained by assuming two causes for light scattering of optical glasses: one is that, when the glass solidifies from supercooled state, thermally fluctuating density and concentration are set frozen before they get settled, the other is that these thermal fluctuations give rise to microscopic traces of strain in the body of the glass when solidifies.
The 3rd order aberrations of telescopic objective are measured by Ronchi and Hartmann tests. The lens tested is a Zeiss semi apochromatic objective ƒ=300mm, ø=180mm. The values of aberration coefficients calculated from the results obtained by Hartmann test by considering the special characteristics of the aberrations and from those obtained by Ronchi test by solving the simultaneous equations are tabulated. As mentioned in the previous reports, Ronchi test is preferable in determining asymmetrical aberration and Hartmann test is suited to determine spherical aberration, but in either method the Gaussian focus must be determined by extrapolation method.